In the production of films, it is known to utilise a calendering device. After leaving the calendering device, the film is passed around one or more take-up rollers. However, German Offenlegungsschrift No. 2204426 discloses that, as the film is passed from the calender to the take-up rollers, wax and other materials from the polyvinyl chloride film are transferred to the take-up rollers.
These deposits formed on the take-up rollers are transferred to the film in the form of a layer having a specific thickness, and they produce specks of condensation product on the film. This phenomenon is known in the art as the so-called "plate-out effect".
In the above-mentioned German Offenlegungsschrift No. 2 204 426, it is suggested that this problem may be overcome by providing an additional metal roller which is coated with a highly absorbent paper. This additional roller is pressed directly against the take-up roller, without the film passing therebetween, and is driven or carried along by the take-up roller. The absorbent paper removes any condensation product from the take-up roller and, in consequence, the film passing over the take-up roller is not contaminated with deposits of condensation products.
In such an arrangement, the metal roller, which is coated with absorbent paper, must be replaced comparatively frequently in order to keep the paper sufficiently absorbent. This is a great inconvenience.
It is also known, from European Patent No. 0 172 924 A2, to keep a web of material in close contact with cooled rollers by directing compressed air thereagainst. The production of a so-called mouldable film is described in this prior specification, which film is retained against a cooling roller by means of an air nozzle immediately after the film has been discharged from a wide-slotted nozzle.
In U.S. Pat. No. 3,893,879, there is disclosed an apparatus for producing an undulatory multi-layered film which is compressed and pressed against a roller by means of compressed-air nozzles.
However, none of these prior art documents disclose any means for preventing the formation of specks of condensation products on films.